1. Field of the Invention
The present invention is directed to an inhalation actuated pulmonary drug delivery device used in the delivery of fluid dispensations from a drug containing canister, the delivery device providing a metered dose of drug or other therapeutic agent when the patient inhales from the device or when the patient compresses a canister section of the device.
2. Brief Description of Related Art
There are a variety of inhalation devices which release aerosol medication, either in a continuous spray or in a predetermined amount of medication, commonly referred to as a metered dose. The spray is applied directly into the patient""s mouth, nasal area or respiratory airways. Typically, these devices are actuated by the pressure applied by the user""s fingers, button action, or other related manual techniques. While there are devices which are activated by the inhalation of the users, some of which are very satisfactory, as with all things, variations or improvements are desirable.
Metered dose aerosol canisters of the medicine to be inhaled into the mouth, nasal areas or respiratory airways are manufactured by a variety of pharmaceutical companies. Therapeutic agents commonly delivered by the inhalation route include bronchodilators (B2 agonists and anticholinergics), corticosteroids, and anti-allergics. Inhalation may also be a viable route for anti-infective, vaccinating, systemically acting and diagnostic agents, as well as anti-leukotrienes, and-proteases and the like. Metered dose aerosols are much the same as non-metered aerosol except that when the valve is depressed, a continuous spray is not discharged. Instead, a predetermined measured volume is discharged as a spray, releasing a fixed amount of medication.
Metered dose inhalers are available in several types. Most frequently, metered dose inhalers comprise a chamber into which a pressure resistant container (canister) is placed. The container is typically filled under super-atmospheric pressures with a product such as a drug dissolved in a liquefied propellant, or micronized particles suspended in a liquefied propellant. The container is fitted with a metering valve. The valve is movable from an outer (charging) position to an inner (discharging) position. A spring bias holds the valve in the charged position until forced to the discharge position. Actuation of the metering valve allows a metered portion of the canister content to be released, whereby the pressure of the liquefied propellant carries the dissolved or micronized drug particles out of the container and to the patient. A valve actuator also functions to direct the aerosol as a spray into the patient""s oropharynx. Surfactants are usually dissolved in the aerosol formulation and can serve the dual functions of lubricating the valve and reducing aggregation of micronized particles. Examples of such metered dose inhalers are disclosed in U.S. Pat. Nos. 5,514,647 entitled xe2x80x9cMetered Dose Inhalerxe2x80x9d; and 5,622,163 entitled xe2x80x9cCounter for Fluid Dispensersxe2x80x9d; and U.S. patent application Ser. No. 09/241,010 filed Feb. 1, 1999 entitled xe2x80x9cMetered Dose Inhaler Agitatorxe2x80x9d (commonly assigned), the disclosures of which are incorporated herein by reference.
Representative of pharmaceutical formulations for use in metered dose inhalers are those described in U.S. Pat. No. 5,190,029. The metered dose inhalers for administering such pharmaceutical formulations are also well known as seen for example in the descriptions given in U.S. Pat. Nos. 3,361,306; 3,565,070; and 4,955,371 which are incorporated herein by reference.
A wide variety of fluid dispensers are known and commercially available to dispense metered proportions of a contained fluid from containers. For example, U.S. Pat. No. 3,749,290 describes a trigger actuated dispensing pump assembled with a fluid container. Upon actuation, a measured proportion of the contained fluid is dispensed from the containers.
xe2x80x9cPumpingxe2x80x9d type inhalers are known in the art. The device may be manually pumped (such as described in U.S. Pat. No. 5,284,132) or a pumping like cycle may be utilized. The medication may also be repeatedly released from a pressurized disposable canister to create repeated sprays or inhalations as needed.
Proper use of these manually actuated devices requires that the spray be activated at the beginning of the inspiratory cycle, so that the medication is carried into the lungs rather than being deposited in the mouth or throat. If this actuation is not correctly coordinated with the inspiratory phase, the metered dose may be deported differently with each actuation acrd potentially compromise the therapeutics and safety of the product.
There are numerous factors leading to poor coordination of actuation of the spray and the inspiration cycle. Included in those factors are the inherent limitations of the users (if any), such as impaired physical abilities associated with geriatric patients or the as-yet-undeveloped skills of children, or their inability of either group to comprehend the correct way to use the device. Recognizing the need for correct and accurately delivered doses in the asthmatics, COPD patients and, as with other patients with other respiratory illnesses, a reliable breath activated device would improve the quality of life for these afflicted people. Examples of breath-activated devices include U.S. Pat. No. 5,069,204 entitled xe2x80x9cInhalerxe2x80x9d and U.S. patent application Ser. No. 09/567,352 entitled xe2x80x9cAn Inhalation Actuated Devicexe2x80x9d, the disclosures of which are herein incorporated by reference.
It is therefore an object of the invention to provide an inhaler that is economical to manufacture, extremely easy to use, and delivers a metered dose of medicine, precise from dose to dose, in response to breath actuation and more particularly, in response to inspiration.
It is therefore a still further object of the present invention to provide an inhaler that is breath-actuated with an option of removing an included dispenser/mouthpiece assembly that is capable of press and breathe dispensing of a medicament.
To attain the objects described above, the present invention is directed to a pneumatically actuated, metered dose dispenser for an aerosol medication. The device has a housing defining a body portion into which the medicine-containing a canister is retained, and a mouthpiece for insertion into a patient""s mouth. A mechanical lever with attached mouthpiece cover operates a compressor pump and after the device is pumped with a charge of compressed gas, maintained in a second chamber, a transfer valve is tripped by the vacuum formed when the user inhales from the device. This causes the compressed gas to enter a second chamber where the drug containing canister is maintained. This effects a depression of the canister valve stem, releasing the drug in an aerosol form. The release of the drug occurs at the same time as inhalation, insuring the delivery of a metered dose of medicine to the target location. In other words, the medicine is not mistargeted to the throat and upper mouth. The device of the present invention is relatively simple to operate, even by young children (6 to 12 years of age), and older patients as well, since inhalation initiates the dispensing of the drug.
An additional embodiment of the present invention is the ability to remove a dispenser/mouthpiece assembly attached within the housing of the device. Upon removal, the assembly can be used as a press and breathe type dispenser. This is advantageous as a backup if the breath-actuation feature of the device fails. In common use, the dispenser/mouthpiece assembly could be removed to replace expended dispensers.